基础dp 记录

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define rep(i,l,r) for (int i=l; i<=r; i++)
typedef long long ll;
using namespace std;
const int N = 5e4+10;
int n, s[N];
int dp[N];

int main(){
    freopen("in.txt","r",stdin);
    //freopen("a.out","w",stdout);
    
    scanf("%d",&n);
    for(int i=1;i<=n;i++) 
        scanf("%d", &s[i]);
    memset(dp,0x3f,sizeof(dp));
    for(int i=1;i<=n;i++) {
        int l = lower_bound(dp+1,dp+1+N,s[i])-(dp);
        dp[l] = s[i];  
    }
    int ans = lower_bound(dp+1,dp+1+N,0x3f3f3f3f)-dp -1;
    cout << ans<<endl;
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
const int maxn = 5e4+10;
int a[maxn],b[maxn],n;
typedef long long ll;

ll solve (int *s)
{
    ll ans =0,res =0;
    for(int i=0;i<n;i++)
    {
        ans+=s[i];
        res = max(res,ans);
        if(ans < 0)
            ans =0;
    }
    return res;
}

int main ()
{

    scanf("%d",&n);
    ll res=0;
    for(int i=0;i<n;i++)
    {
         scanf("%d",&a[i]);
         b[i] = -a[i];
         res += a[i];
    }
    ll ans1= solve(a),ans2=solve(b);
    res= max(ans1,res+ans2);
    printf("%lld\n",res);
    return 0;
}